Compact bar code scanner with scan mirror jointly movable with drive component

ABSTRACT

Several different embodiments are disclosed of a simple, compact bar code scanner which is capable of scanning in any one of several modes, a linear scan mode for scans along a single axis, an omnidirectional scan mode for scans with consecutive scan lines which are angularly displaced relative to each other, or a raster scan mode for scans with consecutive scan lines along a first scan axis which are displaced relative to each other along a second perpendicular axis. In a preferred embodiment, the compact bar code scanner is used in a small housing mounted on an index finger of an operator such that the natural pointing direction of the index finger aims the scanner. In one embodiment, a high frequency flexural member, with a scanning mirror and permanent magnet mounted thereon, is supported by a low frequency flexural member. An x drive coil is positioned by the permanent magnet, and with an applied high frequency x drive signal, causes the high frequency flexural member, with the permanent magnet means and scanning mirror mounted thereon, to torsionally oscillate at the frequency of the x drive signal. A y drive coil is also positioned by the permanent magnet, and with an applied low frequency y drive signal, causes the low frequency flexural member to oscillate to cause low frequency y scanning of the scanning mirror, thereby resulting in a raster scan pattern. With an applied high frequency y drive signal, the y coil causes the high frequency flexural member to oscillate at a high frequency to cause high frequency y scanning of the mirror, thereby resulting in an omnidirectional scan patterns.

This application is a division of U.S. application Ser. No. 08/820,047,filed Mar. 18, 1997, now allowed, which is a division of U.S.application Ser. No. 08/696,112, filed Aug. 13, 1996, now U.S. Pat. No.5,614,706, which is a continuation of U.S. application Ser. No.08/467,648, filed Jun. 6, 1995, now abandoned, which is a division ofU.S. application Ser. No. 08/228,172, filed Apr. 15, 1994, now U.S. Pat.No. 5,543,610, which is a continuation of U.S. application Ser. No.07/884,734, filed May 15, 1992, now abandoned. This application isrelated to U.S. Pat. Nos. 5,693,929; 5,825,013; 5,874,720; 5,917,173 and5,923,025.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a compact bar code scanningarrangement, and more particularly pertains to a compact bar codescanning arrangement which is simple, capable of producing severaldifferent types of scanning patterns, and does not utilize a relativelybulky motor-driven construction. In a preferred embodiment, the compactbar code scanner is used in a small housing mounted on an index fingerof an operator such that the natural pointing direction of the indexfinger aims the scanner.

In general, it would be desirable to provide a compact bar code scannerwhich eliminates the need for bulky motor-driven constructions and iscapable of achieving a high speed 250-300 Hz scan motion.

The present invention provides a compact bar code scanner which iscapable of scanning in any one of several modes, a linear scan modewhich scans along a single axis, an omnidirectional scan mode whichscans with consecutive scan lines which are angularly displaced relativeto each other, such as a Lissajous scan pattern, or a raster scan modewhich scans with consecutive scan lines along a first scan axis, and theconsecutive scan lines are displaced relative to each other along asecond perpendicular axis. With a Lissajous scan pattern, scans areperformed according to the combination of two x and y sinusoidal drivesignals. In the special case wherein the frequency of the x drive signalf_(x) =f_(y), the frequency of the y drive signal, the Lissajous scan isa circular scan pattern, and when f_(x) ≠f_(y), many different complexscan patterns can be generated depending upon the relationship of f_(x)to f_(y).

2. Discussion of the Prior Art

Various optical readers and optical scanning systems have been developedheretofore for reading bar code symbols appearing on a label or on thesurface of an article. The bar code symbol itself is a coded pattern ofindicia comprised of a series of bars of various widths spaced apartfrom one another to bound spaces of various widths, with the bars andspaces having different light-reflecting characteristics.

The scanning of bar code patterns has become more complex as bar codepatterns have become both more complex and more compact. A typical barcode pattern includes lines and spaces of different widths extending inan x direction, and can be scanned by one or more linear scans in the xdirection. Moreover, because the direction of the scan is not alwaysprecisely aligned with the direction of the bar code pattern, morecomplex omnidirectional scanning patterns are sometimes used, whereinconsecutive scan lines are angularly displaced relative to one anotherto form a complex omnidirectional scanning pattern. Two dimensional (2D)bar code patterns (Code 49) have also been introduced wherein, inaddition to a typical bar code pattern having lines and spaces ofvarying widths along an x direction, typical bar code patterns arestacked one upon the other in the y direction to form the 2D bar codepattern. Accordingly, scanning of a 2D bar code pattern is more complex,and requires a raster type of scan wherein consecutive x direction scansare displaced in the y direction by the spacing between stacked rows ofthe 2D bar code pattern to form a raster scan.

The readers and scanning systems electrooptically transform the graphicindicia into electrical signals, which are decoded into alphanumericalcharacters that are intended to be descriptive of the article or somecharacteristic thereof. Such characters are typically represented indigital form and utilized as an input to a data processing system forapplications in point-of-sale processing, inventory control, and thelike. Scanning systems of this general type have been disclosed, forexample, in U.S. Pat. Nos. 4,251,798; 4,369,361; 4,387,297; 4,409,470;4,760,248; and 4,896,026, all of which have been commonly assigned tothe same assignee as the present application.

As disclosed in some of the above patents, one embodiment of such ascanning system resides, inter alia, in a portable laser scanner whichis grasped and hand-held by a user, which is designed to allow the userto aim the scanner, and more particularly a light beam emanatingtherefrom, at a target bar code symbol to be read.

In prior art bar code scanners, the light source in a laser scanner istypically a gas laser or semiconductor laser. The use of a semiconductordevice such as a laser diode as the light source in scanning systems isespecially desirable because of their small size, low cost and low powerrequirements. The laser beam is optically modified, typically by a lens,to form a beam spot of a certain size at the target distance. It ispreferred that the beam spot size at the target distance beapproximately the same as the minimum width between regions of differentlight reflectivity, i.e., the bars and spaces of the symbol.

Bar code symbols are formed from bars or elements that are typicallyrectangular in shape with a variety of possible widths. The specificarrangement of elements defines the character represented according to aset of rules and definitions specified by the code or "symbology" used.The relative size of the bars and spaces is determined by the type ofcoding used, as is the actual size of the bars and spacers. The numberof characters per inch represented by the bar code symbol is referred toas the density of the symbol. To encode a desired sequence ofcharacters, a collection of element arrangements are concatenatedtogether to form the complete bar code symbol, with each character ofthe message being represented by its own corresponding group ofelements. In some symbologies a unique "start" and "stop" character isused to indicate where the bar code begins and ends. A number ofdifferent bar code symbologies exist. These symbologies include UPC/EAN,Code 39, Code 128, Codabar, and Interleaved 2 of 5.

For the purpose of this discussion, characters recognized and defined bya symbology shall be referred to as legitimate characters, whilecharacters not recognized and defined by that symbology are referred toas illegitimate characters. Thus, an arrangement of elements notdecodable by a given symbology corresponds to an illegitimatecharacter(s) for that symbology.

In order to increase the amount of data that can be represented orstored on a given amount of surface area, several new bar codesymbologies have recently been developed. One of these new codestandards, Code 49, introduces a "two-dimensional" concept by stackingrows of characters vertically instead of extending the barshorizontally. That is, there are several rows of bar and space patterns,instead of only one row. The structure of Code 49 is described in U.S.Pat. No. 4,794,239, which is hereby incorporated by reference.

A one-dimensional single-line scan, as ordinarily provided by hand-heldreaders, has disadvantages in reading these two-dimensional bar codes;that is, the reader must be aimed at each row individually. Likewise,the multiple-scan-line readers produce a number of scan lines at anangle to one another so these are not suitable for recognizing a Code 49type of two-dimensional symbols.

In the scanning systems known in the prior art, the light beam isdirected by a lens or similar optical components along a light pathtoward a target that includes a bar code symbol on the surface. Thescanning functions by repetitively scanning the light beam in a line orseries of lines across the symbol. The scanning component may eithersweep the beam spot across the symbol and trace a scan line across andpast the symbol, or scan the field of view of the scanner, or both.

Scanning systems also include a sensor or photodetector which functionsto detect light reflected from the symbol. The photodetector istherefore positioned in the scanner or in an optical path in which ithas a field of view which extends across and slightly past the symbol. Aportion of the reflected light which is reflected by the symbol isdetected and converted into an electrical signal, and electroniccircuitry or software decodes the electrical signal into a digitalrepresentation of the data represented by the symbol that has beenscanned. For example, the analog electrical signal from thephotodetector may typically be converted into a pulse width modulateddigital signal, with the widths corresponding to the physical widths ofthe bars and spaces. Such a signal is then decoded according to thespecific symbology into a binary representation of the data encoded inthe symbol, and to the alphanumeric characters represented thereby.

The decoding process in known scanning systems usually works in thefollowing manner. The decoder receives the pulse width modulated digitalsignal from the scanner, and an algorithm implemented in softwareattempts to decode the scan. If the start and stop characters and thecharacters between them in the scan are decoded successfully andcompletely, the decoding process terminates and an indicator of asuccessful read (such as a green light and/or an audible beep) isprovided to the user. Otherwise, the decoder receives the next scan,performs another decode attempt on that scan, and so on, until acompletely decoded scan is achieved or no more scans are available.

Such a signal is then decoded according to the specific symbology into abinary representation of the data encoded in the symbol, and to thealphanumeric characters so represented.

Laser scanners are not the only type of optical instrument capable ofreading bar code symbols. Another type of bar code reader incorporatesdetectors based upon charge coupled device (CCD) technology. In suchreaders, the size of the detector is larger than or substantially thesame as the symbol to be read. The entire symbol is flooded with lightfrom the reader, and each CCD cell is sequentially read out to determinethe presence of a bar or a space. Such readers are lightweight and easyto use, but require substantially direct contact or placement of thereader on the symbol to enable the symbol to properly read. Suchphysical contact of the reader with the symbol is a preferred mode ofoperation for some applications, or as a matter of personal preferenceby the user.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea compact bar code scanning arrangement. In a preferred embodiment, thecompact bar code scanner is used in a small housing mounted on an indexfinger of an operator such that the natural pointing direction of theindex finger aims the scanner.

A further object of the subject invention is the provision of a compactbar code scanning arrangement which is simple, capable of producingseveral different types of scanning patterns, is capable of achievinghigh scanning rates, and does not utilize a relatively bulkymotor-driven construction.

The present invention provides a compact bar code scanner which indifferent embodiments is capable of scanning in any one of severalmodes, a linear scan mode in which it scans along a single axis, anomnidirectional scan mode in which it scans with consecutive scan lineswhich are angularly displaced relative to each other in anomnidirectional scan pattern, such as a Lissajous scan pattern, or araster scan mode in which it scans with consecutive scan lines along afirst scan axis, and the consecutive scan lines are displaced relativeto each other along a second perpendicular axis.

In accordance with several embodiments disclosed herein, the presentinvention provides a compact bar code scanner in which a flexural memberis supported at one end in a cantilever fashion by a base, and mountsthereon a permanent magnet and a scanning mirror which has a scanningbeam directed thereon, as from a visible laser diode. A drive coil ispositioned adjacent to the permanent magnet, and during operation aperiodically changing drive signal introduced into the coil induces aperiodically changing magnetic field. The periodically changing magneticfield causes the flexural member, with the permanent magnet and scanningmirror mounted thereon, to oscillate at the frequency of theperiodically changing drive signal, thereby causing a linear scanning ofthe scanning beam. For efficiency of operation, the resonant mechanicalfrequency of the flexural member with the scanning mirror and permanentmagnet mounted thereon is designed to be at or near the frequency of theperiodically changing drive signal.

In general, the embodiments disclosed herein are designed to operate ator near their resonant frequencies. However, the embodiments do not haveto operate precisely at or near their resonant frequencies, and this isparticularly true of the torsional mode embodiments.

In accordance with several embodiments disclosed herein, the permanentmagnet is encircled by the drive coil, and the permanent magnet ismounted on the flexural member with an axis extending substantiallycentrally through its North and South poles also extending substantiallyperpendicular to the surface of said flexural member.

In accordance with a second embodiment disclosed herein, the bar codescanner as described hereinabove causes high frequency x scanning of thebeam, which can be generated by any suitable source such as a visiblelaser diode, and the bar code scanner further includes a y scanningmechanism. The y scanning mechanism includes a separate y scanningmirror positioned to receive the high frequency x scanned beam. The yscanning mechanism includes a low frequency y flexural member supportedat one end in a cantilever fashion by a base, and a high frequency yflexural member supported in cantilever fashion by the low frequency yflexural member. The y scanning mirror and a y drive permanent magnetare mounted on the high frequency y flexural member for movementtherewith. A y drive coil is positioned by the y drive permanent magnet,and during operation a periodically changing y drive signal introducedinto the y coil induces a periodically changing magnetic field. When alow frequency y drive signal is introduced into the y drive coil, themagnetic field generated thereby causes the low frequency y flexuralmember to oscillate at a low frequency to cause low frequency y scanningof the second y scanning mirror to generate a raster scanning pattern.When a high frequency y drive signal is introduced into the y coil, thehigh frequency y flexural member oscillates at a high frequency to causehigh frequency y scanning of the second y scanning mirror to generate anomnidirectional scanning pattern. In this embodiment, each permanentmagnet is encircled by each drive coil, and each permanent magnet ismounted on each flexural member with an axis extending substantiallycentrally through its North and South poles also extending substantiallyperpendicular to the surface of the flexural member on which thepermanent magnet is mounted.

A mass is preferably mounted on the low frequency y flexural member totune the resonant frequency thereof to be at or near the low frequency ydrive signal for efficient operation.

In accordance with a third disclosed embodiment, a compact bar codescanner has a low frequency y flexural member supported at one end in acantilever fashion by a base, and a permanent magnet is mounted thereonfor movement therewith. A high frequency x flexural member is supportedin cantilever fashion by the low frequency flexural member. A permanentmagnet and a single scanning mirror are mounted on the high frequency xflexural member for movement therewith, and a scanning beam is directedonto the scanning mirror. An x drive coil is positioned by the permanentmagnet mounted on the high frequency x flexural member, and duringoperation a high frequency periodically changing x drive signalintroduced into the x drive coil causes the high frequency x flexuralmember to oscillate at the high frequency of the x drive signal, therebycausing a high frequency x scanning of the scanning beam. A y drive coilis positioned adjacent to the permanent magnet mounted on the lowfrequency y flexural member, and during operation a low frequencyperiodically changing y drive signal introduced into the y drive coilcauses the low frequency y flexural member to oscillate at the lowfrequency of the y drive signal, thereby causing a low frequency yscanning of the scanning beam, thereby resulting in the generation of araster scanning pattern.

In this embodiment also, a mass is preferably mounted on the lowfrequency y flexural member to tune the resonant frequency thereof to beat or near the low frequency y drive signal, and the high frequencyflexural member is supported in cantilever fashion by the mass. Theresonant mechanical frequency of the high frequency x flexural memberwith the scanning mirror and permanent magnet mounted thereon is alsodesigned to be at or near the frequency of the periodically changing xdrive signal. Each permanent magnet is encircled by each drive coil, andeach permanent magnet is mounted on each flexural member with an axisextending substantially centrally through its North and South poles alsoextending substantially perpendicular to the surface of the flexuralmember on which the permanent magnet is mounted. In this embodiment, aflexural y damping member is secured to the low frequency y flexuralmember to damp higher frequency oscillations thereof.

Fourth, fifth and sixth embodiments of a compact bar code scannerinclude a flexural member supported at one end in a cantilever fashionby a base, with the flexural member being able to flex in bothorthogonally oriented x and y directions. A single scanning mirror ismounted on the flexural member for movement therewith, and a scanningbeam is directed thereon.

In the fourth embodiment, an x drive permanent magnet is mounted on theflexural member for movement therewith, and an x drive coil ispositioned adjacent to the x drive permanent magnet. During operation, aperiodically changing x drive signal introduced into the x drive coilcauses the flexural member to oscillate at the frequency of theperiodically changing x drive signal, thereby causing an x scanning ofthe scanning beam. A y drive permanent magnet is also mounted on theflexural member for movement therewith, and a y drive coil is positionedadjacent to the y drive permanent magnet. During operation, aperiodically changing y drive signal introduced into the y drive coilcauses the flexural member to oscillate at the frequency of theperiodically changing y drive signal, thereby causing a y scanning ofthe scanning beam. Each of the x drive and y drive permanent magnets ispositioned at one end of respectively the x and y drive coils, and eachof the x drive and y drive permanent magnets is mounted on the flexuralmember with an axis extending substantially centrally through its Northand South poles also extending substantially parallel to central axes ofrespectively the x and y drive coils. The flexural member is supportedat one end in a cantilever fashion in a vibrational damping material onthe base, to damp undesired frequencies thereof.

In the fifth embodiment, a single permanent magnet is mounted on theflexural member for movement therewith. A pair of x drive coils ispositioned by the permanent magnet, and during operation a periodicallychanging x drive signal introduced into the pair of x drive coils causesthe flexural member, with the permanent magnet and scanning mirrormounted thereon, to oscillate at the frequency of the periodicallychanging x drive signal, thereby causing an x scanning of the scanningbeam. A pair of y drive coils is also positioned by the permanentmagnet, oriented orthogonally with respect to the pair of x drive coils,and during operation a periodically changing y drive signal introducedinto the pair of y drive coils causes the flexural member, with thepermanent magnet and scanning mirror mounted thereon, to oscillate atthe frequency of the periodically changing y drive signal, therebycausing a y scanning of the scanning beam. The permanent magnet ispositioned at one end of the pairs of x and y drive coils, and thepermanent magnet is mounted on the flexural member with an axisextending substantially centrally through its North and South poles alsoextending substantially parallel to the central axes of the pairs of xand y drive coils.

In the sixth embodiment, a drive coil is mounted on the flexural member.A pair of x drive permanent magnets is positioned by the drive coil, anda pair of y drive permanent magnets is also positioned by the drivecoil, oriented orthogonally relative to the pair of x drive permanentmagnets, and during operation a periodically changing drive signalintroduced into the coil causes the flexural member, with the drive coiland scanning mirror mounted thereon, to oscillate in both x and ydirections at the frequency of the periodically changing drive signal,thereby causing a scanning of the scanning beam. The drive coil ispositioned at one end of the pairs of x drive and y drive permanentmagnets with an axis extending substantially centrally therethrough alsoextending substantially parallel to the central axes of the pairs of xand y drive permanent magnets.

In accordance with seventh, eighth and ninth embodiments disclosedherein, a low frequency flexural member is supported in cantileverfashion by a base, and a high frequency flexural member is supported incantilever fashion by the low frequency flexural member for movementtherewith. A scanning mirror is mounted on the high frequency flexuralmember for movement therewith, and a scanning beam is directed thereon.A permanent magnet means, which might include either a single magnet orfirst and second magnets with the poles of the first and second magnetsbeing oriented orthogonally with respect to each other, is mounted onthe high frequency flexural member for movement therewith. An x drivecoil is positioned by the permanent magnet means, and a periodicallychanging high frequency x drive signal introduced into the x drive coilcauses the high frequency flexural member, with the permanent magnetmeans and scanning mirror mounted thereon, to torsionally oscillate atthe frequency of the periodically changing x drive signal, therebycausing an x scanning of the scanning beam. A y drive coil is positionedby the permanent magnet means, and during operation a periodicallychanging y drive signal introduced into the y coil induces aperiodically changing magnetic field. When a low frequency y drivesignal is introduced into the y drive coil, the low frequency flexuralmember oscillates at a low frequency to cause low frequency y scanningof the scanning mirror. When a high frequency y drive signal isintroduced into the y coil, the high frequency flexural memberoscillates at a high frequency to cause high frequency y scanning of themirror.

In the seventh and ninth embodiments disclosed herein, the permanentmagnet means is mounted on the high frequency flexural member with anaxis extending substantially centrally through North and South polesthereof also extending substantially parallel to the central axis of they drive coil and substantially perpendicular to the central axis of thex drive coil.

In the seventh, eighth and ninth embodiments, the permanent magnet meansis positioned at one end of the x drive coil, and is mounted on the highfrequency flexural member with an axis extending substantially centrallythrough a North and South pole thereof also extending substantiallyperpendicular to the central axis of the x drive coil, for operation ina torsional twisting mode.

For efficiency of operation, the torsional resonant mechanical frequencyof the high frequency flexural member with the scanning mirror andpermanent magnet means mounted thereon is designed to be at or near thefrequency of the periodically changing x drive signal. Moreover, thebending resonant mechanical frequency of the high frequency flexuralmember with the scanning mirror and permanent magnet means mountedthereon is designed to be at or near the frequency of the periodicallychanging high frequency y drive signal. Also, a mass is mounted on thelow frequency flexural member to tune its resonant frequency to the lowfrequency y drive signal, and the mass also mounts the high flexuralmember in cantilever fashion.

In the seventh embodiment, the permanent magnet means is positioned inan air gap between the x and y drive coils, which are mounted with theircentral axes substantially colinear.

In the eighth disclosed embodiment, an x drive coil is mounted side byside with the y drive coil with the central axes thereof being parallel,and the permanent magnet means is mounted by one end of the x and ydrive coils. The center of the permanent magnet means is positionedopposite the central axis of the x drive coil, which induces torsionaltwisting of the permanent magnet and high frequency flexural member andx scanning of the beam. A poled end of the permanent magnet means ispositioned opposite the central axis of the y drive coil, which induceseither low frequency y scanning by low frequency flexing of the lowfrequency flexural member, or high frequency y scanning by highfrequency flexing of the high frequency flexural member.

In the eighth disclosed embodiment, the permanent magnet means ismounted on the high frequency flexural member with an axis extendingsubstantially centrally through its North and South poles also extendingsubstantially perpendicular to the central axes of the x and y drivecoils.

In the ninth embodiment, a mass is mounted on the low frequency flexuralmember to tune the resonant frequency thereof, and the mass is mountedto the base by a low frequency flexural member which extends fromopposite sides of the mass to the base, and torsionally flexes duringlow frequency y scanning operations.

The present invention also provides a bar code scanning system in whicha first housing is adapted to be worn on a user's finger. The firsthousing includes a symbol detection means for generating a light beamdirected toward a symbol to be read on a target and for receivingreflected light from the symbol to produce an electrical signalcorresponding to the intensity of the reflected light, and also a switchfor energizing the scanning beam. The housing is mounted on the fingerin a position to project a scanning beam forwardly generally in thenatural pointing direction of the finger. The electrical signal istransferred from the first housing to a second housing which includes asignal processor for processing the electrical signal to generatetherefrom a digitized signal descriptive of the bar code symbol. Thesecond housing is mounted on the user's wrist, and includes therein adecoder for translating the digitized signal into data represented bythe bar code symbol.

In an alternative embodiment, the present invention provides a bar codescanning system in which a first housing is adapted to be mounted on auser's finger to project a scanning beam forwardly generally in thenatural pointing direction of the finger. The first housing includes asymbol detection means for generating a light beam directed toward asymbol to be read on a target and for receiving reflected light from thesymbol to produce an electrical signal corresponding to the intensity ofthe reflected light, and a switch for energizing the light beam. Thefirst housing also includes therein a signal processor for processingthe electrical signal to generate therefrom a digitized signaldescriptive of the bar code symbol, which is transferred from the firsthousing. In greater detail, the digitized signal is transferred from thefirst housing to a second housing mounted on the user's wrist whichincludes therein a decoder for translating the digitized signal intodata represented by the symbol.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing objects and advantages of the present invention for acompact bar code scanning arrangement may be more readily understood byone skilled in the art with reference being had to the followingdetailed description of several preferred embodiments thereof, taken inconjunction with the accompanying drawings wherein like elements aredesignated by identical reference numerals throughout the several views,and in which:

FIG. 1 is a perspective view of an exemplary embodiment of a simple andcompact linear scanning arrangement pursuant to the teachings of thepresent invention which is driven without a traditional bulky motor;

FIG. 2 illustrates a universal pattern scanning arrangement pursuant tothe present invention which operates partially according to theprinciple of operation of the scanner of FIG. 1, and which is capable ofscanning at a relatively high frequency in an x direction, and of eithernot being driven in y scanning to generate a linear x scanning pattern,or of scanning at two different frequencies in a y direction, arelatively high frequency for omnidirectional scanning patterns, or arelatively low frequency for raster scanning patterns;

FIG. 3 illustrates a third embodiment of the present invention which issomewhat similar in operation to the embodiment of FIG. 2, but wherein yand x scanning mechanisms are mounted in a unitary assembly on a commonbase, and a single scan mirror performs both x and y scanningoperations;

FIGS. 4, 5 and 6 illustrate three related embodiments of the presentinvention which are capable of producing virtually any different type ofscanning pattern, including linear, omnidirectional such as Lissajous,or raster scanning patterns, and which utilize a single scanning mirrormounted at the free end of an electromagnetically driven central rod,which is capable of oscillating in two orthogonal x and y directions;

FIG.7 and 8 illustrate two related universal scanning embodiments of thepresent invention which include a base which mounts in cantileverfashion a low frequency y flexural member which mounts at its free endin cantilever fashion a high frequency flexural member, and wherein an xdrive coil is driven with a constant high frequency drive signal toproduce x scan deflections, and a second y drive coil uses a drivesignal which is one of two fixed frequencies, a low frequency drivesignal for raster scanning patterns, or a high frequency drive signalfor omnidirectional scanning patterns;

FIG. 9 illustrates a preferred embodiment of a universal compact barcode scanning arrangement pursuant to the present invention in which abase includes a low frequency y flexural mounting for a mass whichprovides a low frequency y scanning motion, and a second flexural memberis cantilever mounted on the mass and mounts at its surface a scanningmirror and a permanent magnet which interacts with an adjacentencircling x driving coil to produce high frequency x scanning movementsand with an adjacent y driving coil to produce either no, or high or lowfrequency y scanning movements;

FIG. 10 illustrates the mode of operation of the x driving mechanism inthe embodiments of FIGS. 7, 8 and 9, in which a permanent magnetinteracts with an adjacent x driving coil;

FIG. 11 illustrates the orientation of the permanent magnet of theembodiment of FIG. 9 relative to the y driving coil, and illustrates themanner in which the permanent magnet interacts with the y driving coil;

FIG. 12 illustrates an arrangement wherein a miniature scanner asdisclosed herein for a bar code reader is mounted within a housingsupported on an index ring mounting on the index finger of an operator,and the electronics in the bar code reader communicates by a short rangeradio transmitter with a receiver which might typically be mounted onthe belt of the operator;

FIG. 13 illustrates an arrangement similar to FIG. 12 wherein aminiature scanner as disclosed herein for a bar code reader is mountedwithin a housing supported on an index ring mounting on the index fingerof an operator, and the electronics in the bar code reader communicatesby a wire with a portable terminal mounted on a wrist band on the wristof the operator; and

FIGS. 14 and 15 illustrate respectively a front perspective view and aside elevational view of a further embodiment of a torsional mode,miniature scanning element pursuant to the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first embodiment of the resent invention for asimple and compact, high speed, linear bar code scanner which is drivenwithout a traditional bulky motor. Referring to FIG. 1, a linearscanning arrangement 10 is provided in which a flexural strip 12 of asuitable flexible material such as Mylar is cantilever mounted to a base14, as by being secured between two halves of the base 14. The flexuralstrip 12 supports thereon a miniature permanent magnet 16 positionedinside a coil 18, with an axis passing centrally through the North andSouth poles of the permanent intersecting the surface of the flexuralstrip 12 substantially perpendicular thereto. The coil 18 is alsosecured to the base 14, and a scan mirror 20 is attached to the free endof the cantilever mounted flexural strip 12. By changing the dimensions(length, width and thickness) or the flexural characteristics of thecantilever mounted strip 12, or the mass of the flexural strip 12, thepermanent magnet 16 and mirror 20, or the distribution of mass on theflexural strip 12, different resonant frequencies can be established forthe vibrating assembly. In general, the natural resonant frequency isdetermined by the size (length, width and thickness) and flexuralstrength of the cantilever mounted member, the distribution of mass, andthe total mass of the vibrating assembly. Formulas are available and areknown in the art to determine the resonant frequency of the vibratingassembly, which can also be tested and developed empirically. When aperiodic drive signal 22, such as a sinusoidal signal, is introducedinto the coil 18, the periodically reversing magnetic field inducedthereby causes the cantilever mounted assembly to oscillate up and down,as shown in FIG. 1. This produces a linear scanning motion of the scanmirror 20, which causes a linear scanning of a beam directed onto themirror by a suitable beam source such as a visible laser diode (VLD) 24.A sinusoidal periodic drive signal causes a periodically reversingmagnetic field to be generated by the coil 18, thus creating moments offorces acting upon the North (N) and South (S) poles of the permanentmagnet 18, to cause the magnet and the flexible strip 12 on which it ismounted, along with the scan mirror 20 (all of which comprise acantilever mounted assembly) to vibrate up and down, perpendicular tothe flat surface of the flexible strip 12, at a frequency dependent uponthe frequency of the periodic drive signal.

In general, and for all of the embodiments disclosed herein, it isdesirable to drive a cantilever mounted assembly or a torsional modemounted assembly with a periodic signal at or near the resonantfrequency of the assembly, and to design the assembly with a naturalresonant frequency as high as possible to achieve high scan rates of upto several hundred hertz (e.g. 500 Hz). However, lower scan rates arealso possible. In general, the chosen scan rate depends upon theparticular application, and a 36 scans per second scan rate is typical,which is generated by a periodic signal of 18 Hz.

It is noted that in the description herein, the descriptions of furtherembodiments often build upon the descriptions of earlier embodiments,and accordingly the descriptions of the details, construction and modeof operation, to the extent they are identical or similar, is generallynot repeated for the additional embodiments.

FIG. 2 illustrates a universal pattern, compact bar code scanningarrangement which operates partially according to the principle ofoperation of the scanner of FIG. 1, and which is capable of scanning ata relatively high frequency in an x direction, and of not scanning in ay direction for production of a linear x scan, or of scanning at twodifferent resonant frequencies in a y direction, a relatively highfrequency or a relatively low frequency. A variety of bar codes anddifferent bar code reading conditions require different types of scanpatterns, such as linear scans, raster scan patterns, or omnidirectionalscan patterns such as Lissajous type scan patterns. The embodiment ofFIG. 2 is capable of producing all of these scan patterns with arelatively simple construction, and includes a double resonantconstruction for producing either a high or low frequency y verticalscan motion.

In the universal scanning arrangement of FIG. 2, a light beam from asuitable source such as a Visible Laser Diode (VLD) 26 is directedinitially onto a high speed horizontal x deflection arrangement 28 whichproduces high speed x scanning deflections of the beam. The x deflectionarrangement 28 can be and preferably is the same as the linear scanningarrangement 10 in FIG. 1. The resultant x scanned beam is then directedto a vertical deflection arrangement 30, which produces either no, orlow or high speed vertical scanning deflections of the beam, providedrespectively for raster and omnidirectional scan patterns. The yscanning arrangement 30 includes a flexible base provided with twodegrees of mechanical freedom to provide two resonant conditions, a lowfrequency y scan for raster patterns, and a high frequency y scan foromnidirectional patterns. The y scanning arrangement is driven by theelectromagnetic forces produced by a coil 44 which encircles a permanentmagnet 42 mounted in the y scanning assembly 30 in a manner similar tothat as explained with reference to the embodiment of FIG. 1.

The y scanning assembly 30 comprises a base 34 which supports acantilever mounted low frequency flexural strip 36 which supports at itsfree end a mass 38, which in turn supports a smaller cantilever mountedhigh frequency flexural strip 40. The flexural strip 40 mounts thereonthe permanent magnet 42 positioned within the coil 44, and a scanningmirror 46 mounted at the free end of the flexural strip 40. In thisarrangement, the mass 38 and all of the structure mounted thereon (40,42, 46) can oscillate on the cantilever mounted low frequency flexiblestrip 36 at a low resonant frequency f_(rL), and the magnet 42 and scanmirror 46 can oscillate on the smaller cantilever mounted high frequencyflexible strip 40 at a high resonant frequency f_(rh). The mass 38 isselected to tune the resonant frequency of the low frequency y flexuralmember to be at or near the low frequency y drive signal for efficientoperation. Similar to the first embodiment, for efficient operation theresonant mechanical frequency of the high frequency y flexural memberwith the y scanning mirror and permanent magnet mounted thereon isdesigned to be at or near the frequency of the periodically changinghigh frequency y drive signal. The resonant frequency of each vibratingassembly is determined in general by the spring constant K of thevibrating member and the mass M and distribution of mass of thevibrating assembly. In the two degree of freedom embodiment of FIG. 2,each of the two vibrating assemblies has a different spring constant K(K₁ and K₂) and a different mass M (M₁ and M₂) and distribution of mass.

Selection of either the low resonant frequency f_(rL) or the highresonant frequency f_(rh) is accomplished by changing the frequency ofthe y periodic drive signal 48 through the y driving coil 44. When thereis no driving current through the y driving coil 44, a laser beam fromthe VLD 26 is incident on the mirror 20 of the scanning assembly 28which produces a fast (about 300 Hz) x scan line, which is directed ontoand reflected by the mirror 46 of the y scanning assembly 30 without anychanges in the scan pattern, thereby producing a linear horizontal scanline. When a low frequency signal 48 is connected to the y driving coil44, it produces a low frequency vertical motion about the low frequencyflexible strip 36, thereby producing a raster pattern. When a highfrequency signal 48 is connected to the y driving coil 40, it produces ahigh frequency vertical motion about the high frequency strip 40,thereby producing an omnidirectional scanning pattern. In the secondembodiment, the scanning movement in the y direction can be designed tobe a desired ratio to the scanning movement in the x direction inaccordance with the desired omnidirectional scan pattern.

FIG. 3 illustrates a third embodiment of the present invention which issomewhat similar in operation to the embodiment of FIG. 2, but wherein yand x scanning mechanisms 56, 58 are mounted in a unitary assembly on acommon base 60, which in a compact or miniaturized scanner can comprisea PC board. For perspective, in one designed embodiment the length ofthe base 60 was 1.1 inches, the height was 0.45 inches, and the widthwas 0.45 inches. The y scanning assembly 56 includes a flexural member62, cantilever mounted to the base 60, which mounts a permanent magnet64 positioned inside a y driving coil 66. The flexural member 62 can befabricated of any suitable material such as Mylar, and includes thereona damping flexural member 68 which can also be fabricated of anysuitable material such as Mylar, which is included to damp higherfrequency modes of oscillation of the y scanning assembly. A mass 70 ismounted at the free end of the cantilever flexural member 62 to tune they scanning assembly to an appropriate low resonant frequency f_(rL).

The x scanning assembly 58 includes a flexural member 72 cantilevermounted to the mass 70 at the free end of the y flexural member 72, andsupports thereon a permanent magnet 74 positioned within an x drivingcoil 76.

A single scan mirror 78 is mounted to the free end of the x flexuralmember 72, such that it is supported to be driven with high frequency xscanning movements and either no y scanning for a linear x scan or witha low frequency y scanning, to produce a raster type of scanningpattern.

Each permanent magnet 64, 74 is encircled by each drive coil 66, 76, andeach permanent magnet is mounted on each flexural member with an axisextending substantially centrally through its North and South poles alsoextending substantially perpendicular to the surface of the flexuralmember on which the permanent magnet is mounted. The feature of a singlescan mirror is particularly advantageous as the small scan mirrors areexpensive. The embodiment of FIG. 3 can produce a linear scan pattern byactuation of only the x scanning assembly 58, or a raster scan patternby actuation of both the y and x drive assemblies 56 and 58, but cannotgenerate an omnidirectional scanning pattern.

FIGS. 4, 5 and 6 illustrate three related embodiments of the presentinvention for a compact bar code scanner which include a flexural membersupported at one end in a cantilever fashion by a base, with theflexural member being able to flex in both orthogonally oriented x and ydirections. A single scanning mirror is mounted on the flexural memberfor movement therewith, and a scanning beam is directed thereon. Theseembodiments are capable of producing virtually any scanning pattern,including linear, omnidirectional such as Lissajous, or raster scanpatterns, and which utilize a single scanning mirror.

In the embodiment of FIG. 4, a scan mirror 82 is mounted at the free endof a flexible shaft 84, the other end of which is flexibly fixed to abase 86 to provide a cantilever type mounting for the flexible shaft,which is capable of vibrating in both x and y directions. Two permanentmagnets 88, 90 are mounted as by short mounting supports 89, 91 to theflexible shaft 84 and are mounted perpendicularly at 90° relative toeach other. In this arrangement, axes extending centrally through both Nand S poles of the permanent magnets 88 and 90 coincide respectivelywith the central axes of x and y driving coils 92, 94. In thisarrangement, each of the coils 92, 94, when driven with a periodic drivesignal, generates an alternately reversing magnetic field, as describedhereinafter with reference to FIG. 10, with the alternately reversingmagnetic field alternately attracting and repelling the pole of thepermanent magnet positioned closest to the coil. A damping material 96such as rubber, silicon, etc. is used to mount and hold the shaft 84 inplace to the base 86 to create a restoring force and to damposcillations thereof.

The embodiments of FIGS. 5 and 6 are similar, and their designs arebased upon the designs of driving cartridges currently utilized to cutmaster records (e.g. 33 or 45 rpm recorded records). These drivingcartridges are produced by manufacturers such as Shure Brothers, Inc.

In the embodiment of FIG. 5, a central shaft 100 is supported in a smallcartridge 102, and supports a small magnet 104 which is positionedcentrally between projecting magnetic cores 105 of two pairs of x and ydriving coils 106, 108, with the pair of x driving coils being orientedorthogonally with respect to the pair of y driving coils.

A single scan mirror 110 is supported at the free end of the shaft 100,and is driven in x and y scanning movements by periodic drive signalsapplied to the x and y driving coils 106, 108.

The embodiment of FIG. 6 is functionally symmetrically opposite to theembodiment of FIG. 5, and includes a single moving coil 110, having aninput 111, which is mounted on a shaft 112 which interacts magneticallywith stationary pairs of opposed x and y permanent magnets 114, 116. Asingle scanning mirror 118 is mounted at the free end of the shaft 112,and is driven in x and y scanning movements by a periodic drive signalapplied to the coil 110.

FIGS. 7 and 8 illustrate two related universal scanning embodiments ofthe present invention. The embodiment of FIG. 7 includes a base 118which mounts in cantilever fashion a relatively wide, low frequency yflexural member 120 which mounts at its free end a mass 122. The mass122 in turn mounts in cantilever fashion a relatively narrow, highfrequency flexural member 124, which supports thereon two mutuallyperpendicular permanent magnets 126, 128 (can also be one T or crossshaped magnet) and a scan mirror 130 which is secured to the inner end(rightmost in FIG. 7) of the magnet 128. The permanent magnet 126 ispositioned adjacent to an x drive coil 132, and the permanent magnet 128is positioned adjacent to a y drive coil 134, with the assembly beingpositioned in the air gap between the two parallel coils 132, 134, whichare driven by two periodic drive signals. The x drive coil 132 is drivenwith a constant high frequency drive signal to produce x scan directiondeflections, and the second y drive coil 134 uses a drive signal whichis one of two fixed frequencies, a low frequency drive signal for araster scan pattern, or a high frequency drive signal for Lissajousscanning patterns.

FIG. 10 illustrates the mode of operation of the x driving mechanism inthe embodiment of FIG. 7 in which permanent magnet 126 interacts withthe x driving coil 132. When the coil 132 has a periodic drive signalapplied thereto, the N and S poles thereof periodically reversethemselves. When the N pole is at the top and the S pole is at thebottom of FIG. 10, as illustrated in FIG. 10, the permanent magnet 126and the flexural member 124 to which it is secured are torsionallytwisted such that the S end of the permanent magnet is twisted towardsthe N pole at top, and the N end of the permanent magnet is twistedtowards the S pole at the bottom. When the poles of the driving coil arereversed and the S pole is at the top and the N pole is at the bottom ofFIG. 10, the permanent magnet 126 and the flexural member 124 aretwisted in an opposite direction such that the N end of the permanentmagnet 126 is twisted towards the S pole at the top, and the S end ofthe permanent magnet 126 is twisted towards the N pole at the bottom.Accordingly, the permanent magnet 126 and the flexural member 124 towhich it is attached, and the scanning mirror 130, are alternatelytwisted and oscillated in clockwise and counterclockwise x scanningmovements.

The y scanning mechanism in the embodiment of FIG. 7 operates in amanner similar to the embodiment of FIG. 4. The permanent magnet 128 ispositioned with an axis extending centrally through the N and S ends ofthe permanent magnet being positioned colinear with the central axis ofthe y drive coil 134. One end of the permanent magnet 128 is positionedclosest to the drive coil, such that as a periodic drive signal reversesthe poles of the coil 134, the end of the magnet 128 closest to coil 134is periodically attracted to and repelled by the reversing poles of thecoil 134, thereby causing either the low frequency flexural strip 120 orthe high frequency flexural strip 124 to bend periodically to produceeither a high frequency scan with a high frequency drive signal or a lowfrequency scan with a low frequency drive signal.

For efficiency of operation, the torsional resonant mechanical frequencyof the high frequency flexural member 124 with the scanning mirror 130and permanent magnets 126, 128 mounted thereon is designed to be at ornear the frequency of the periodically changing x drive signal.Moreover, the bending resonant mechanical frequency of the highfrequency flexural member 124 with the scanning mirror 130 and permanentmagnets 126, 128 mounted thereon is designed to be at or near thefrequency of the periodically changing high frequency y drive signal.Also, the mass 122 is selected to tune the resonant frequency to the lowfrequency y drive signal.

In the seventh embodiment, the permanent magnets 126, 128 are positionedin an air gap between the x and y drive coils 132, 134, which aremounted with their central axes substantially colinear.

The embodiment of FIG. 8 includes a base 118, a low frequency y driveflexural member 120, mass 122, and a high frequency x drive flexuralmember 124, similar to the embodiment of FIG. 7. The drive arrangementincludes a single horizontally positioned permanent magnet 136, with ascan mirror 137 mounted thereon, which is positioned adjacent to and iscontrolled and driven in scanning movements by two adjacent x and ydrive coils 140, 138 which are wound on a soft metal core. The x drivecoil 140 is positioned opposite the center of the permanent magnet andcontrols the horizontal x scanning motion, with the operation thereofbeing similar to the operation of the embodiment of FIG. 7 (x scan). They drive coil 138 is positioned parallel to and side by side with thefirst coil opposite to one poled end of the permanent magnet andcontrols the y vertical scanning motion. As the polarity of the y drivecoil is periodically reversed, the poled end of the permanent magnet infront of coil 138 is periodically attracted to and repelled by thealternating polarity of the x drive coil 138 which produces either lowfrequency y scanning by low frequency flexing of the low frequencyflexural member 120, or high frequency y scanning by high frequencyflexing of the high frequency flexural member 124.

FIG. 9 illustrates a preferred embodiment (best mode) of a compact barcode scanning arrangement pursuant to the present invention in which amass 186 is mounted to a flexural mount 184, with each end thereofextending from an opposite side of the mass 186, which is periodicallytorsionally flexed back and forth to provide a slow vertical y scanningmotion. In a preferred embodiment, a single flexural member 184 extendsbetween two base mounts 182, with the mass 186 being secured to thesingle flexural member, as on the top thereof. Moreover, the singleflexural member could be a suitable torsional rod attached directly tothe base mounts 182, or attached indirectly to the base mounts 182 bysuitable torsional springs. A second flexural member 188 is cantilevermounted on the mass 186, and mounts at its surface a permanentmagnet.190 and a scanning mirror 192. The permanent magnet 190 interactswith an adjacent y driving coil 194 and an adjacent encircling x drivingcoil 196, with the magnet 190 interacting with the coils 194 and 196 ina manner as illustrated respectively in FIGS. 11 and 10.

FIG. 11 illustrates the orientation of the permanent magnet 190 relativeto the y driving coil 194, and illustrates the manner in which permanentmagnet 190 interacts with the y driving coil 194. As a periodic drivesignal is applied to drive coil 194, the poles of driving coil 194periodically change from N to S. When the y drive coil 194 has its Npole at the left end and its S pole at the right end, as illustrated inFIG. 11, the magnet 190 is repelled thereby and is displaced away fromthe coil 194, and when the poles of the coil 194 are reversed, with theS pole at the left end and the N pole at the right end, the magnet 190is attracted thereby and is displaced towards the coil 194, thusresulting in the magnet 190 being periodically oscillated away andtowards the coil y drive 194 to produce a y scanning movement. When alow frequency y drive signal is utilized, the low frequency y driveflexural members 184 support a low frequency y drive oscillation ofmirror 192, and when a high frequency y drive signal is utilized, thehigh frequency flexural member 188 supports a high frequency y driveoscillation.

The high frequency x drive coil 196 produces alternating reversals ofthe poles of the coil 196, and operates in a manner similar to theembodiment of FIG. 7 (x drive). When an N pole is present at the end ofcoil 196 adjacent to the permanent magnet 190, the S end of thepermanent magnet is attracted thereto and the N end of the permanentmagnet is repelled thereby, thus producing a periodic clockwise andcounterclockwise torsional flexing of the flexural member 188, toproduce a high frequency x scanning of the flexural member 188 and themirror 192 mounted thereon.

In summary, two coils 194, 196, with mutually perpendicular axes, arelocated adjacent the magnet/mirror assembly, with coil 194 positioned incoil 196, and provide magnetic force which causes the entire assembly tooscillate in three modes, including a high frequency horizontaloscillation mode, either alone, or in a high frequency verticaloscillation mode or in a low frequency vertical oscillation mode.

In the ninth embodiment, the mass 186 tunes the torsional resonantfrequency of the low frequency flexural member 184 which extends fromopposite sides of the mass to the base, and torsionally flexes duringlow frequency y scanning operations.

FIG. 12 illustrates an arrangement wherein a miniature scanner 201 asdisclosed herein for a bar code reader is mounted within a housing 200supported on an index ring mounting 202 on the index finger 204 of anoperator. A trigger switch 206 is provided on the side of the housing200 which is activated by the operator's thumb 208 to actuate thescanner 201. The electronics in the bar code reader communicates thedata it has acquired by a short range radio transmitter 210 in thehousing 200 to broadcast to an antenna 212 of a receiver in anassociated control unit 214, which might typically be mounted on thebelt 215 of the operator. The control unit 214 in the second housingtypically would include a display, a keyboard, or a touch screenfunctioning as a display/keyboard, similar to that illustrated in FIG.13. In an alternative embodiment, the scanner could be voice activatedwith a voice recognition means installed in either the housing 200 orthe control unit 214.

A typical prior art bar code reader includes a bar code scanner, asignal digitizer, and a decoder. The bar code scanner generates a lightbeam directed toward a symbol to be read on a target and receivesreflected light from the symbol to produce an analog electrical signalcorresponding to the intensity of the reflected light. The signaldigitizer includes a signal processor for processing the analogelectrical signal to generate therefrom a digitized signal descriptiveof the bar code symbol. The decoder decodes or translates the digitizedsignal into data represented by the symbol.

In the embodiment of FIG. 12, the finger mounted housing 200 includestherein the bar code scanner 203 for producing an analog electricalsignal and a signal digitizer 203 for generating therefrom a digitizedsignal descriptive of the bar code symbol. The digitized signal is thentransmitted by radio transmission to a decoder 213 located in thecontrol unit 214.

FIG. 13 illustrates an arrangement similar to FIG. 12 wherein aminiature scanner 201 as disclosed herein for a bar code reader ismounted within a housing 200 supported on an index ring mounting 202 onthe index finger 204 of an operator. A trigger switch 206 is provided onthe side of the housing 200 which is activated by the operator's thumb208, or alternatively a voice activated arrangement could be utilizedtherein. The electronics in the bar code reader communicates the analogsignal produced by the scanner 201 by a wire 218 with a portable controlterminal 220 mounted on a wrist band 221 in a wristwatch like manner onthe wrist of the operator. The portable terminal 220 typically includesan LED display 222, an array 224 of entry keys, and an antenna 226 forcommunicating with a central computer. The analog signal on wire 218 isdirected to a signal digitizer 227 located in the control terminal 220which digitizes the analog signal, and the output digitized signaltherefrom is directed to a decoder 228 also located in the controlterminal 220. The output of the decoder, which is data represented bythe scanned bar code symbol, is then transmitted by 226 to the centralcomputer. Accordingly, the embodiment of FIG. 13 also differs from theembodiment of FIG. 12 by placing the digitizer 227 in the associatedcontrol terminal 220 rather than in the housing 200.

FIGS. 14 and 15 illustrate respectively a front perspective view and aside elevational view of a further embodiment 230 of a torsional mode,miniature scanning element pursuant to the present invention. Theembodiment of FIGS. 14 and 15 advantageously can be operated from a verylow frequency of about 1-2 Hz to a relatively high frequency ofapproximately 160-180 Hz without any physical changes or mechanicaladjustments or tuning. The embodiment of FIGS. 14 and 15 is mechanicallybalanced, and the vertical mounting of a torsional flexural supportmember 232 therein advantageously does not result in any drooping of thetorsional flexural support member and the components supported thereby.In this embodiment, a -vertically mounted strip 232 of flexible materialis attached and mounted at the top and bottom thereof to the front of asmall magnetic coil 234. A permanent magnet 236 is mounted horizontallyon one side of the flexible strip and a mirror 235 is mounted to theopposite side thereof. The permanent magnet and scanning mirror can beeither attached directly to the flexible strip 232 or preferably by sometype of holder 238. When an AC current is applied to the coil 234,interaction of the changing magnetic field of the coil 234 and themagnet 236 causes the flexible strip 232 to oscillate horizontally in atorsional mode.

The flexible strip 232 can be fixed to the coil by a holder 240 whichmight be mounted either directly to the front of the coil 234, asillustrated in FIG. 14, or with an intermediate shock absorber material242, illustrated by a spring-like member in FIG. 15, in order to providemechanical protection in the event of dropping of the scanning assembly230. The holder 240 might have a transparent shield 244 mounted on thefront thereof to provide a sandwich-type of structure for protection ofthe mirror. In order to enhance performance and save energy, the coilpreferably has a core 246 of soft steel or similar material.

While several embodiments and variations of the present invention for acompact bar code scanning arrangement are described in detail herein, itshould be apparent that the disclosure and teachings of the presentinvention will suggest many alternative designs to those skilled in theart.

What is claimed is:
 1. In a bar code reader having a light emitter foremitting a light beam toward a bar code symbol for reflection therefrom,and a detector for detecting light reflected from the symbol, a compactbar code symbol scanning assembly, comprising:a) a stationary support;b) a scan mirror for reflecting the light beam incident thereon towardthe bar code symbol to be scanned; c) a flexure having stationaryportions fixed to the stationary support, and a movable portion betweenthe stationary portions and operatively connected to the scan mirror tosupport the scan mirror for movement relative to the stationary support;and d) an energizable electromagnetic drive for moving the scan mirror,including a permanent magnet for generating a permanent magnetic field,and an electromagnetic coil for generating a magnetic field thatinteracts with the permanent field in response to an energizing drivesignal through the coil, one of the magnet and the coil being mountedon, and symmetrically arranged relative to, the scan mirror for jointbalanced movement with the scan mirror relative to the stationarysupport to scan the light beam over the symbol.
 2. The assembly of claim1; and further comprising a holder operatively connected to the scanmirror for holding the scan mirror, and wherein the movable portion ofthe flexure is operatively connected to the holder.
 3. The assembly ofclaim 2, wherein the scan mirror has a front reflecting surface on whichthe light beam is incident, and an opposite rear surface on which theholder is connected.
 4. The assembly of claim 2, wherein said one of themagnet and the coil is mounted on the holder.
 5. The assembly of claim2, wherein the scan mirror, the holder and said one of the magnet andthe coil are suspended from and by the flexure for joint oscillatingmovement; and wherein the drive oscillates the scan mirror, the holderand said one of the magnet and the coil.
 6. The assembly of claim 5,wherein the scan mirror, the holder and said one of the magnet and thecoil are oscillated about an axis along an arcuate path.
 7. The assemblyof claim 5, wherein the flexure includes a first part that extends fromone location on the stationary support to the holder, and a second partthat extends from another location on the stationary support to theholder, and wherein the locations are spaced apart from each other. 8.The assembly of claim 1, wherein the flexure includes a taut spring. 9.The assembly of claim 8, wherein the spring is a leaf spring.
 10. In amethod of reading bar code symbols by emitting a light beam toward asymbol for reflection therefrom, and by detecting light reflected fromthe symbol, a method of scanning comprising the steps of:a) reflectingthe light beam incident on a scan mirror toward the symbol; b)supporting the scan mirror for movement relative to a stationary supportby fixing stationary portions of a flexure to the stationary support,and by connecting a movable portion of the flexure to the scan mirror;and c) moving the scan mirror by generating a permanent magnetic fieldwith a permanent magnet, by generating a magnetic field that interactswith the permanent field by conducting a drive signal through anelectromagnetic coil, by mounting one of the magnet and the coil on thescan mirror, and by symmetrically arranging said one of the magnet andthe coil relative to the scan mirror, for joint balanced movement withthe scan mirror relative to the stationary support to scan the lightbeam over the symbol.
 11. The method of claim 10; and further comprisingthe step of holding the scan mirror with a holder, and the step ofconnecting the movable portion of the flexure to the holder.
 12. Themethod of claim 11, wherein the mounting step includes the step ofmounting said one of the magnet and the coil on the holder.
 13. Themethod of claim 12, wherein the mounting step includes the step ofsuspending the scan mirror, the holder and said one of the magnet andthe coil from and by the flexure for joint oscillating movement; andwherein the moving step includes the step of oscillating the scanmirror, the holder and said one of the magnet and the coil.
 14. Themethod of claim 13, wherein the oscillating step is performed byoscillating the scan mirror, the holder and said one of the magnet andthe coil about an axis along an arcuate path.